doc/go1.4.txt: fmt: document printing of &map rather than just pointer

CC=golang-codereviews
https://golang.org/cl/152160043

doc/go1.4.txt

@@ -21,6 +21,7 @@ cmd/go: compile and link all _test.go files during 'go test', even in packages w
 asm: make textflag.h available outside of cmd/ld (CL 128050043)
 crypto/tls: add support for ALPN (RFC 7301) (CL 108710046)
 crypto/tls: support programmatic selection of server certificates (CL 107400043)
+fmt: print type *map[T]T as &map[k:v] (CL 154870043)
 encoding/gob: remove unsafe (CL 102680045)
 misc: deleted editor support; refer to https://code.google.com/p/go-wiki/wiki/IDEsAndTextEditorPlugins instead (CL 105470043)
 net/http: add Request.BasicAuth method (CL 76540043)